1. Field of the Invention
This invention relates to improvements in methods and circuits for driving inductive loads, or the like, to which it is desired to apply signals having a fast rise time, and more particularly to improvements in methods and circuits for driving inductive loads of the type used in conjunction with a write head of a disk drives, or the like.
2. Relevant Background
Most computer systems include one or more associated disk drives, which may be built into the computer system, or which may be external to the computer system for connection via known means to the system. Typically, disk drives have at least one rotating magnetic medium and associated head mechanisms that are carried adjacent the material. The heads are radially positionable to selectively write information to, or read information from, precise positions on the disk medium. Such disk drives may be, for example, so-called hard disk drives, floppy drives, or the like.
Data is written to the associated data disk by applying a series of signals to the write head according to the digital information to be stored on the magnetic disk media. The write head has a coil and one or more associated pole pieces that are located in proximity to the disk media. As the magnetic flux changes in the head, the magnetic domains of the magnetic media of the disk are aligned in predetermined directions for subsequent read operations. Typically, a small space separates each magnetic domain transition to enable successive transitions on the magnetic media to be distinguished from each other.
Since the disk is moving relative to the head, it can be seen that if the small space separating each magnetic domain transition is not sufficiently wide, difficulty may be encountered in distinguishing successive magnetic transitions. This may result in errors in reading the data contained on the disk, which is, of course, undesirable.
Meanwhile, as computers are becoming faster and faster, it is becoming increasingly important to increase the speed at which data can be written to the disk media. However, since the data signals are in the form of square wave transitions, if the rise time of the leading edges of the square waves is large, the small space between magnetic media transitions also becomes large, which reduces the effective rate at which data can be accurately written and read. Since the write head assembly includes at least one coil, forcing the current to rise rapidly, or to reverse flux directions, within the write head is difficult.
In the past, data writing circuits used to supply such write signals to the heads include preamplifier circuits to drive the current through selected legs of an "H-bridge" circuit, which is capable of allowing relatively fast current reversals for accurate data reproduction.
What is needed, therefore, is a method and circuit for driving an inductive load of the type used in conjunction with a write head of a disk drive for association with a computer or the like, with a signal that enables a maximum flux reversal rate in the driver coil.